High-power, short-pulse laser irradiance can be used to write and store data within a glass substrate. The irradiance induces a long-lived lattice perturbation at its focus, which derives from non-linear, two-photon absorption by the substrate. In some cases, the lattice perturbation has the optical properties of a nano-grating embedded within the substrate at the point where the irradiance is imaged. Data written to a glass substrate in this manner can be read back using a polarized optical beam to interrogate the various grating-like perturbations formed within it.